Abstract
The visual system is tuned for rapid detection of faces, with the fastest choice saccade to a face at 100ms. Familiar faces have a more robust representation than do unfamiliar faces, and are detected faster in the absence of awareness and with reduced attentional resources. Faces of family and close friends become familiar over a protracted period involving learning the unique visual appearance, including a view-invariant representation, as well as person knowledge. We investigated the effect of personal familiarity on the earliest stages of face processing by using a saccadic-choice task to measure how fast familiar face detection can happen. Subjects made correct and reliable saccades to familiar faces when unfamiliar faces were distractors at 180ms—very rapid saccades that are 30 to 70ms earlier than the earliest evoked potential modulated by familiarity. By contrast, accuracy of saccades to unfamiliar faces with familiar faces as distractors did not exceed chance. Saccades to faces with object distractors were even faster (110 to 120 ms) and equivalent for familiar and unfamiliar faces, indicating that familiarity does not affect ultra-rapid saccades. We propose that detectors of diagnostic facial features for familiar faces develop in visual cortices through learning and allow rapid detection that precedes explicit recognition of identity.
Highlights
As social animals we rely on interaction with conspecifics for survival
While we glance at unfamiliar faces for signs of threat or interest—during brief interactions—we spend most of our time looking at the faces of our relatives, friends, and loved ones
We ran two pilot experiments with 4 participants each and obtained comparable results to previous studies using the same unfamiliar faces and objects that Crouzet et al [4] employed in their experiment
Summary
As social animals we rely on interaction with conspecifics for survival. The complexity of our brains might have stemmed from the processing demands of living in groups [1,2,3]. The face represents one of the most efficient means to convey and receive social information. The human visual system appears to be tuned to these informative stimuli. Behavioral evidence suggests that familiar faces have a more robust representation in the brain [6], strengthened and stabilized over the course of repeated interactions, with underlying distributed and specialized pathways for different aspects of face perception [7,8]. PLOS ONE | DOI:10.1371/journal.pone.0136548 August 25, 2015
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